Circuit boards are used extensively and in various applications throughout the electronics industry that permeates today's technologically advancing world. Advances in the electronics industry generally parallel increased levels of integration of the individual electronic components such as integrated circuits, and the assemblies, subassemblies and packages such as circuit boards or other multi-component circuit members. A circuit board generally includes a plurality of various components and networks that host signal pathways whose characteristic mode or transmission may require either or both guided media (copper electrical trace, glass or polymer optical waveguide) and unguided media (radio frequency (Rf) antenna, free-space optical (FSO) or other electromagnetic signaling, magnetic coupling, or transformer). Most prominent and important among the components are integrated circuit (IC) chips also known simply as chips that contain many forms of circuits and various methods for signal pathways. Integrated circuits chips consist of an array of integrated circuits formed on a semiconductor wafer and are then singulated into individual die and thus also are referred to as semiconductor chips. Such ICs contain lithographically patterned transistors, interconnections, passive components (inductor, resistor, capacitor, etc.,) and are monolithic in structure and may involve electrical, optical, optoelectronic, or passive functions and interconnections. The degree of integration of a circuit board is determined by the number of integrated circuit chips packaged and placed with other thermal, mechanical and connector components that the network of a circuit board accommodates.
Conventional circuit board and/or flex circuit designs allow only for the placement of IC chips on opposed sides of the board. This limits the component density achievable per unit area of the circuit board. As the electronics industry continues to evolve, higher component densities in smaller spaces are needed to address the demand for higher performance networks and more portable applications. In order to achieve a higher density of components and interconnections per unit area, various approaches have been taken but are still limited to providing active circuit elements such as integrated circuit chips, on the opposed surfaces of the circuit board or other circuit member. For example, the stacking of bare ICs or the use of multi-chip module (MCM) packaging was developed as a packaging solution to directly integrate at the chip level. Another approach to chip density packaging is wafer scaled integration to directly integrate active circuits at the wafer level. The wafer scaled integration is further limited as it can only integrate IC chips formed of the same technology. Other approaches such as developing three dimensional chip stacking techniques have been undertaken, however, chip stacking techniques tend to limit the electrical interconnects between IC and thermal dissipation and further that input/output (I/O) signal pathways through or around the perimeter of the IC inhibit achieving higher density circuitry or networks. Flexible circuit boards are known and can advantageously adapt to various configurations, but their flexibility is limited by the flexibility of the components formed on the circuit boards and the flexibility and durability of the interconnects that couple the circuit components. Flexible circuit boards have similarly limited component densities, as above.
It would therefore be advantageous to further increase component per unit area density and therefore integration levels of a circuit board or other circuit member, by embedding integrated circuit chips within such an electronic circuit member, and additionally advantageous to do so with a flexible circuit board.